Responding to geopolitical crises is a major issue in national security. The way states react often depends on how their leaders perceive the nature and severity of the crisis. The Islamic Republic of Iran’s presence in Iraq, in response to the rise of ISIS, has been one of the most significant reactions of Iranian leaders to a geopolitical crisis in recent years. This development has also had wide effects across the Middle East. Using documented evidence and primary sources, and applying documentary research and post‑event analysis, this article examines why and how Iran entered Iraq’s internal crisis. It also investigates what this military and political presence has meant for Iran’s national interests. The findings suggest that Iran’s involvement was shaped by several factors. These include geopolitical considerations, the need to neutralize nearby threats, maintaining the regional balance of power, and supporting a friendly government. In this context, Iran adopted a combined approach described as leading from the front and leading from behind. Drawing on realism and the concept of Forward defense, the study argues that this presence helped protect Iran’s national security and territorial integrity. It also reduced the geopolitical threat of Salafi radicalism in West Asia and helped prevent a regional shift in the balance of power against Iran.